Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.
Coal separation involves the use of coarse circuits to remove coarse waste and fines circuits to remove fine or particulate waste. Much of this waste is mineral matter that, in the context of coal, is left behind when the coal is burnt. This mineral waste matter is traditionally known in the coal industry as “ash”. Ash content is an approximation of mineral matter content, but the ash content is generally quoted in coal processing because it is much more convenient and less expensive to analyse for. The term “ash content” is hereinafter used in this specification to refer to the mineral matter content.
In many coal preparation plants, fines circuits are generally poorly controlled in relation to the coarse circuits and total plant yield is thus reduced as a result. The total plant yield of coal can be improved if the ash content of the slurry can be determined at each stage of the coal separation process, especially when passing through the fines circuits. This would allow greater control over the separation process and hence improve the efficiency of the plant.
One known coal slurry ash analyser relies on nuclear sources to measure the ash content in the coal solids. However, this analyser suffers from operational problems as it is adversely affected by any entrained air in the slurry and requires frequent calibration. Furthermore, installing this analyser in a coal plant is prohibitive due to its cost and requires the implementation of health and safety measures due to the nuclear source in the analyser. As a consequence, few coal plants have installed this analyser.